The Martensitic Transition and Magnetocaloric Effect of Mn-Poor MnCoGe Melt-Spun Ribbons

We investigated the martensitic transition and the magnetic properties of Mn_1-xCoGe melt-spun ribbons. The as-prepared Mn_1-xCoGe ribbons crystallize in austenite hexagonal phase with a textured structure. The postannealing process promotes the formation of the martensitic phase and homogenization of the alloy, resulting in a first-order magnetostructural transition in the annealed ribbons, and thus a giant magnetocaloric effect. The magnetic entropy change around the transition reaches 19 J/kgK for a magnetic field change of 0-5 T. Furthermore, it is found that the hysteresis loss around the magnetostructural transition is negligible in present annealed ribbons, which would facilitate the application of Mn_1-xCoGe alloys.